Switch frog for the overhead conductors of electric traction systems



Oct. 1. 1940. T. c. BROOM ET AL swrrcn inoe FOR wm pvsnamn CONDUCTORS 0F ELECTRIC TRACTION SYSTEMS Filed Jan. 20, 1939 6 Sheets-Sheet l I nventor M 5% MYW Attorney Oct. 1. 1940.

r. c. BROOM Er AL SWITCH FROG FOR THE OVERHEAD CONDUCTORS 0F ELECTRIC TRACTION SYSTEMS Filed Jan. 20, 1939 6 Sheets-Sheet 2 A ttorney Oct. 1. 1940. T. c. BRQOM ET AL swrrcn mos FOfl ME OVERHEAD CONDUCTORS 0F ELECTRIC TRACTION SYSTEMS 6 Sheets-Sheet 3 Filed Jan. 20, 1939 A t lorney 0a. 1.1940 BROOM Em 2,216 290 SWITGH FROG FOR was OVERHEAD counuc'rons 0F ELECTRIC TRACTION SYSTEMS Filed Jan. 20, 19 39 6 Sheets-Sheet 4 o'i a Li.

Inventor fimwmv fiwm Attorney 06L 1; 1940. 1' c BROOM AL 2,216,290 SWITQH 330G FOR THE'OVERHEAD CONDUCTORS 0F ELECTRIC TRACTION SYSTEMS Filed Jan. 20, '1939 6 Sheets-Sheet 5 WBMW 9 m M MM+QMMM Attorney Inventor snow SYSTEMS Oct. 1. 1940. r. c. BROOM ET AL SWITCH FROG FOR THE OVERHEAD CONDUCTORS OF ELECTRIC TBA Filed Jan. 20, 1939 6 Sheets-Sheet 6 A ttorn y Patented Oct. 1, 1940 PATENT OFFICE SWITCH FROG FOR THE OVERHEAD CON- DUCTORS CF ELECTRIC TRACTION SYS- TEMS Talbot Cottom Broom,

Huyton, and Howard Jenkins Powell, Liverpool, England, assignors to British Insulated Cables Limited, Prescot,

Lancashire, England, a British company Application January 20, 1939, Serial No. 251,960 In Great Britain December 1, 1937 4 Claims.

This invention relates to switch frogs which are used in overhead electric traction systems. Such .a switch frog comprises a pivoted switchplate carrying a movable tongue which is nor- 5 mally set in a position which permits movement of a current collector in the most frequently used path and is adapted to be moved in a horizontal plane into another position when the collector is required to move in another path. Hereinafter the first-mentioned position of the switch frog will be referred to as the primary position, and its positionwhen operated will be referred to as the secondary position.

A switch frog is generally one of two kinds according to whether it is intended for use at a branch or a cross-over point. When intended for use at a branch position the switch frog is so designed that it may be set to permit the passage of a current collector either along the main line or along a branch line to or from the main line. The body of the frog is generally provided with a fixed leg in alignment with each ,of the main conductors and the branch conductor extending from the frog, and a pivoted switchplate adapted to be moved in a horizontal plane so as to bring a movable tongue into alignment with two of the fixed legs whereby the current collector may be directed in the required path. In a switch frog of this kind the switch-plate may be formed with one or two tongues. Where only one tongue is provided this performs the double function of completing the path from the branch to the main conductor in one position of :the switch-plate and closing the gap in the main 35 conductor in the other position. Where two tongues are provided on the switch-plate each tongue serves to complete one of the paths when the switch-plate is in one position and is inoperative when the switch-plate is in the other position.

When intended for use at a cross-over the switch-plate is of the kind in which a movable tongue selectively provides for passage of a current collector in either of two intersecting paths. The body of a switch frog of the cross-over type is usually provided with two pairs of fixed legs, eachpair being in alignment with one of the intersecting conductor paths. A switch plate pivotally mounted on the underside of the frog so as to turn in a horizontal plane about the point of intersection carries a movable tongue which, in the primary position, is in alignment with one pair of fixed legs, thus completing the most frequently used path, and which may be moved into the secondary position to complete the less freeffects movement of the switch-plate from the primary to the secondary position. The coupling also ensures that the biassing restraint serves to return the switch-plate to the primary position when the applied force is removed. The configuration of the crank and the associated parts is such that when the switch-plate is in the primary position the only or principal force which can be applied to the crank from the switch-plate acts towards the axis of rotation of the crank. Such a force will have no component which can serve to move the crank, and, therefore, there can be no accidental displacement of the switch-plate by a force which may be applied to it otherwise than by means of the crank.

In one form of the arrangement the connection between the crank and the switch-plate is in the form of a connecting rod which is pivotally joined to both these members. The point of engagement between the connecting rod and the crank is so located that when the switch-plate is in the primary position the connecting rod is in a dead centre position with reference to the axis of rotation of the crank. This prevents displacement of the switch-plate by a force which may be applied to it otherwise than through the connecting rod.

In another form of construction the crank makes sliding engagement with the switch-plate so that the rotary movement of the crank produces a turning movement of the switch-plate about its pivot from one position to the other. The orientation of the crank, with reference to the switch-plate pivot, and the location of the point of engagement between the crank and switch-plate is such, when the latter is in the primary position, that the only or principal force which can be applied to the crank from the switch-plate is in a line which passes through the axis of rotation of the crank. Such a force has no component which can serve to move the crank, and the switch-plate is thus locked against movement by such an accidentally applied force. In a preferred form of construction of this kind, the crank is provided with a crank-pin which engages in a slot formed in the switch-plate and extending in a line which passes through the switch-plate pivot.

In a preferred arrangement the crank is in the form of a pulley which is rotatable in a horizontal plane by means of a chain or a similarly flexible member which engages the periphery of the pulley. The force required to move the switchplate into the secondary position is applied to one end of the chain and the other end is engaged by a biassing means which may be a tension spring anchored to the body of the frog.

The invention isfurther described hereinafter with reference, by way of example, to the accompanying drawings, wherein:

Figure I is a view from above of a switch frog for use at a branch point, having operating means in accordance with the invention, the switchplate being in a primary position;

Figure II is a side view of the arrangement shown in Figure I;

Figure III is a view from below of the switchfrog illustrated in Figures I and II, but with the switch-plate in the secondary position;

Figure IV is a view from above of a switch frog for use at a branch point, having another form of operating means in accordance with the invention, the switch-plate being in a primary position;

Figure V is a side view of the arrangement shown in Figure IV;

Figure VI is a view from below of the switch frog illustrated in Figures IV and V, but with the switch-plate in the secondary position;

Figure VII is a view from above of a switch frog for use at a branch point, having a modified form of the operating ineans represented in Figures IVVI, the switch-plate being in a secondary position; and

Figure VIII is a view from above of a switch frog of the cross-over type having a form of operating means in accordance with the invention.

The switch frog which is illustrated in Figures I, II and III comprises a body portion I having three fixed legs, 2, 3 and 4, each provided on the lower side thereof with a conducting blade 5, 6 and I respectively. The body I is provided with apertured lugs 8 which permit it to be suspended at any desired branch point in an overhead conductor system. Two of the legs 2 and 3 are adapted to be in alignment with the main overhead conductor. The third leg 4 is set at a more or less acute angle to the leg 3 being thereby adapted to be in alignment with the branch conductor. On the underside of the body I is pivotally mounted a switch-plate 9 which is movable in a horizontal plane about a point I9 near the inner ends of the branch tongue l and the adjacent main tongue 3. On the underside of the switchplate 9 are formed two tongues I I and I2. In one position of the switch-plate the tongue I2 is in alignment with the conducting blades 5, 6 on the two main legs 2 and 3, and in the other position of the switch-plate the tongue I I is in alignment with the conducting blades 5, I on the first main leg 2 and the branch leg 4 respectively. The normal or primary position of the switchplate is that shown in Figure 1 in which the path is set by the tongue I I from the main to the branch conductor. The operated or secondary position is that shown in Figure III in which the tongue I2 completes the main path.

On one side of the body I remote from the branch leg 4 and adjacent that end of the switchplate 9 which is remote from its pivot point II) there is formed a vertical machined face I3 which provides a seating for a bracket 14 in which is mounted a grooved pulley I5. The pulley I5 is rotatable about a vertical axis I6 in a horizontal plane which is slightly above the plane of movement of the switch-plate 9, as shown in Figure II. A short length of chain I'I passes around a portion of the grooved pulley surface between the pulley and the body of the frog, and is fixed at about its central point to the pulley so that the latter may be positively rotated by moving the chain longitudinally. One end of the chain is attached to a tension spring I8 anchored to a lug I9 mounted on the body of the frog, and the other end of the chain is provided with a loop 20 for manual operation or is connected to any desired form of manually or mechanically operating means. The tension spring I8 supplies a biassing restraint to return the switch-plate to the primary position when the chain I1 is relieved of the operating tension. In an approximately central position there is provided on the switch-plate 9 an upstanding pivot pin 2| and a downwardly projecting pin 22 is located eccentrically on the underside of the pulley l5. The pivot pins 2| and 22 are interconnected by means of a connecting rod 23, the effect of which is to translate the retary motion of the pulley I5 into an oscillatory motion of the switch-plate 9 about its point ll] of pivotal engagement with the body of the frog.

In the primary position as represented in Figure I the switch-plate is held against a stop by the action of the tension spring I8, the movable tongue I I completing the path between one main and the branch conductor. The location of the eccentric pivot pin 22 is such that in this position the connecting rod 23 extends across the axis I6 of the pulley thereby occupying a dead centre position. Thus any tendency for the switchplate to move if subjected to a side pull by a current collector passing over the tongue II to or from the branch conductor is prevented. By applying an operating force to the chain I! the pulley I5 is rotated in the direction of the arrow against the biassing restraint of the tension spring I 8 until its movement is arrested by the engagement of a projecting surface 24 formed on the switch-plate with an abutment 25 formed on the body of the frog. The switch-plate is now in the secondary position as represented in Figure III, the path between the main leg 2 and branch leg 4 being broken by the displacement of the movable tongue II and the second movable tongue I2 being in the correct position to complete the main conductor path. As soon as the chain is released the mechanism returns under the action of the tension spring to the primary position.

The primary and secondary positions may be conveniently reversed by providing an alternative point of attachment for the chain to the grooved pulley and substituting a connecting rod of a different length. Thus, for instance, the chain I l is disconnected from the pulley which is thereupon rotated until the eccentric pivot pin 22 occupies a position, indicated by the broken circle 26, which is in alignment with the axis of the pulley and the pivot pin 2|. A short connecting rod now interconnects the pivot pin 22 in this new position 26 and the pivot pin 2i, and the chain I? is reconnected with the pulley so that the biassing restraint offered bythe spring I8 retains the switch-plate in the position represented in Figure LII, this being now the primary position. The short connecting rod now occupies a dead centre position thus serving to prevent accidental movement of the switch-plate as in the previous. instance, but does not extend across the axis of the pulley. An operative force applied to the. chain ll against the restraining effect of the spring l8 rotates the pulley in the direction indicated by the arrow, and by virtue of the connecting rod the switch-plate is moved into the position represented in Figure I, this being now the secondary position. i

The switch frog may also be conveniently set for operation from the opposite side by mounting the pulley bracket [4 on another machined face 2i formed on that side of the body of the frog and attaching the tension spring to another anchorage 28 provided also on that side of the frog. In order to prevent accidental displacement of the chain from the grooves in the pulley a guard plate 29 attached to the pulley. bracket is arranged with one end extending over the face of the groove.

The switch-frog illustrated in Figures IV, V and VI is also adapted for use atabranch point and is in general similar tothat already described, those features which remain unchanged being for the purpose of convenience given the same reference numbers. In this construction, however, the connection between the pulley l5 and the switch-plate 9 is effected by means other than the connecting rod of the previous construction. The eccentrically located crank pin 22 projecting downward from the pulley I5 is fitted with a roller 30 which engages in a slot 3| in a plate 32 formed on the side of the movable switch-plate 9. The operating chain I! extends round a portion of the groove in the pulley l3 and terminates therein. On the pulley axis slightly above its plane of rotation is arranged a second pulley 33 of smaller diameter and rotatable with the first mentioned pulley. A short length of chain 34 is fixed atone end to this second pulley 33, passing partly around the periphery thereof and beingattached at the other end to the free end of the tension spring l8.

The tension spring l8 serves as a biasing means as inthe previously described arrangement to return the switch-plate to the primary position when the operating chain I1 is released. In Figure IV the switch-plate 9 .is shown in a primary position, the main conductor path being completed between the conducting blades 5 and t on two main legs 2 and 3 by the movable tongue l2. In Figure VI the switch-plate 9 is shown in the secondaryposition, the main conductor path being broken and a path completed between the main. and branch conductors by the alignment of the other movable tongue H with conducting blades 5 and I on the legs 2 and 4. i

As the pulley I5 is: rotated by a force applied to -the operating chain I! the crank pin roller 3E bears against that side 35 of the slot 3| which is nearest the pulley axis and as it rotates around that axis the roller 30 moves along the slot 3| in a direction away from the switch plate pivot 10. The switch-plate is consequently turned about its pivot fromthe primary position (Figure IV) into the secondary position (Figure VI). When the operating force is removed the biassing spring- I8 returns the crank pin 22 to the initial position (Figure IV). During, this movement the crank pin roller 30 bears against that side 36 of the slot 3| which is remote from the axis of the pulley and as the pulley rotates around that axis the crank pin 22 moves along the slot 3| in a direction toward the switchplate pivot. ID. The switch-plate consequently is turned about the pivot Hi until the primary position (Figure IV) is reached. Thus the effect of the connection between the crank pin 22 and the slot 3| is to translate the rotary motion of the pulley it into an oscillatory motion of the switch-plate 9 about its point of engagement N) withthe body of the frog. The slot 3| is soformed thatits centre line passes through the centre of the pivot Ill about which the switchplate turns. When the switch-plate is in the primary position (Figure IV) the line passing through the axis of the pulley and the crank pin is atright angles to the centre line of the slot so that the only or principal force that can .beapplied from the switch-plate to the crank pin acts towards the axis of the pulley. Such a force cannot cause rotation of the pulley with consequent accidental displacement of the switchplate from the primary position, so that the switch-plate is effectively locked in this position. I

The primary and secondary positions of the switch-plate may be readily reversed in this form as in the previously described arrangement. To effect this the operating and biasing chains Hand 34 respectively are disconnected from the pulleys and are re-attached after thepulleys have been rotated through about half a revolution so that the new points of attachment of the chains are almost diametrically opposite their original points of attachment. The crank'pin 22 and roller 3t will be in a new position which is approximately 180 from. its previous position. In this position the roller ttnow engages another slot and thereby operates the movable switch-plate in a manner similar to that previously described excepting. that the primary and secondary positions are reversed.

This arrangement is represented in Figure VII, which represents the switch-frog in a secondary position in which the main path is set. The location :of the crank pin roller in the primary position is indicated by the broken circle 38. i The switch-plate is conveniently provided with two slots, namely, theslot 3|, the function of which has been already described and a second slot 31 which is used under theconditions now being describedw In the secondary position shown the pulley i5 has been turned in the direction of the arrow by the application of an operating force to the operating chain ll. The crank pin 22 has moved fromthe normal position 38 to the position indicated, moving at the same time in the slot 31 towards the pivot Hi and at the same time causing the switch-plate 3 to turn about this pivot into the secondary position. The position 3B of the crankpin 22 and the direction of-the centre line of the slot 31 are such that in the primary position the only or principal force which can be transmitted from the switch-plate to the crank pin will be directed towards the axis of the pulley, thereby ensuring that the switchplate will not be accidentally displaced from that position. The portion of the switch-plate in which the slots 3i and 3i are formed may be a separate member attachable on whichever side of the frog is convenient. Furthermore, the two slots may be formed in separate members, either of which may be mounted on the frog at either side thereof and in accordance with the selec- .tion of the primary and secondary positions. The pulley may be mounted on either side of the frog inthe manner previously described. i

In- Figure VIII is illustrated the application of the invention to a switch frog of the crossover type. The body 39 of the frog is provided with four fixed legs, 40, 4|, 42 and 43 related in pairs in alignment with two conductor paths which intersect at a central point. Mounted on the underside of the frog is a switch-plate 44 adapted to turn in a horizontal plane between two extreme positions about a pivot 45 located at the above-mentioned point of intersection. The switch-plate carries on its underside a tongue which in one position is in alignment with one pair of fixed legs 40, 42 and in the other is in alignment with the other pair of fixed legs 4|, 43. In the arrangement shown the switch-plate is in a primary position, the path being completed between the fixed legs 40 and 42. A pivot pin 46, remote from the switch-plate pivot 45, formed on the switch-plate is connected by means of a connecting rod 47 with a crank pin 48 arranged eccentrically on a pulley 49. The pulley 49 is rotatable in a horizontal plane in a bracket 50 attached to the side of the frog and is operated by means of a chain 5| engaging its grooved periphery. A biassing chain 52 is fixed at one end 53 to a radius arm formed on a second pulley 54 arranged above and co-axially rotatable with the first-mentioned pulley 49. The biassing chain passes partly round the second pulley 54 and is engaged by a tension spring 55 anchored to the frog. The connecting rod 4'! transmits the rotational movement of the pulley 49 into an oscillatory movement of the switch-plate 44 about its pivot 45, moving the switch-plate out of the primary position shown into the secondary position when a force is applied to the operating chain 5! and returning it to this position under the biassing restraint of the spring 55 when this force is removed. The limits of movement of the switch-plate are provided by two curved slots 56 formed in the body of the frog, the pivot pin 46 projecting into one of them and a pin 5'! projecting into the other at the other end of the frog. The pins 46 and 51 engage the ends of the slots 56 in the extreme primary and secondary positions. An upstanding projection 58 formed on the radius arm is adapted to engage an abutment 59 on the pulley bracket 50 in the primary position, thereby providing a further means for limiting the movement of the switch-plate.

As in the previously described arrangements the switch-plate is locked in the primary position against accidental displacement by the arrangement of the connecting rod in a dead centre position. The primary and secondary positions are also reversible by using a connecting rod of different length and adjusting the operating mechanism in the manner previously described. The operating means may be mounted on the most convenient side of the switch frog. Furthermore, the connection between the switch frog and the operating crank may be of a sliding nature similar to that described with reference to Figures IV and VII.

The improved mechanism possesses a number of advantages. The switch-plate can be operated from any convenient direction on either side of the frog, and either of the two positions can be selected as the primary position. The operating chain can be pulled at any angle to the frog within a wide range in View of the tangential engagement between the chain and pulley. The switch-plate is eifectively locked in the primary position. Furthermore, since the point of engagement of the operating means with the switch-plate is at a distance from its axis of movement, the operating forces are low, so that there is minimum wear of the moving parts and adjustment between the tongues is less frequently required. In this arrangement also the plane of the operating chain is only very little above the level of the conductor so that there is a minimum turning moment tending to tilt the frog when the chain is subjected to operating tension. These two advantages last mentioned are still more evident in the case of two switch-frogs which have their moving parts mechanically connected so as to be operated simultaneously by the same chain.

What we claim as our invention is:

1. A trolley switch frog comprising an elongated body portion, an elongated switch-plate pivoted to the said body portion for angular movement relative thereto in a horizontal plane between primary and secondary positions, a wheel mounted on the body portion adjacent the region of maximum movement of the switch-plate for rotation about a vertical axis, a crank pin on said wheel, a coupling between said pin and said switch-plate such that when the switch-plate is in the primary position the pin is in dead centre position to thereby lock the switch-plate in said primary position, a flexible tension member trained around said wheel, whereby to run the latter and move the plate from the primary to the secondary position, and a restoring spring anchored at one end to said body portion, the other end of the spring being secured to a flexible tension member trained around said wheel to exert a continuous torque thereon tending to move the switch-plate from the secondary to the primary position, the diameter of the crank pin circle being greater than the distance between the positions of the crank pin when the switch-plate is in the primary and the secondary positions, whereby rotation of the wheel through an angle less than 180 effects movement of the plate from the primary to the secondary position, said restoring spring always being efiective to urge the plate toward the primary position.

2. A trolley switch frog comprising an elongated body portion, an elongated switch-plate pivoted to the said body portion for angular movement relative thereto in a horizontal plane between primary and secondary positions, a wheel mounted on the body portion adjacent the region of maximum movement of the switch-plate for rotation about a vertical axis, a crank pin on said wheel, a connecting rod pivoted to said pin and to said switch-plate such that when the switch-plate is in a primary position the pin is in dead centre position, a flexible tension member trained around said wheel, whereby to turn the latter and move the plate from the primary to the secondary position, and a restoring spring anchored at one end to said body portion, the other end of the spring being secured to a flexible tension member trained around said wheel to exert a continuous torque thereon tending to move the switch-plate from the secondary to the primary position, the diameter of the crank pin circle being greater than the travel of the end of the connecting rod pivoted to the switch-plate as the latter moves between primary and secondary position, whereby rotation of the wheel through an angle less than 180 efiects movement of the plate from the primary to the secondary position, said restoring spring being always efiective to urge the plate toward its primary position.

3. A trolley switch frog comprising an elongated body portion, an elongated switch-plate pivoted to the said body portion for angular movement relative thereto in a horizontal plane between primary and secondary positions, a wheel mounted on the body portion adjacent the region of maximum movement of the switch-plate for rotation about a vertical axis, a crank pin on said wheel, there being a slot in the side of the switch-plate adjacent the crank pin, the crank pin engaging the walls of the slot to move the switch-plate relative to the said body portion and such that when the switch-plate is in the primary position the pin is in a dead centre position, a flexible tension member trained around said wheel whereby to turn the latter and move the plate from the primary to the secondary position, and a restoring spring anchored at one end to said body portion, the other end of the spring being secured to a flexible tension member trained around said wheel to exert a continuous torque thereon tending to move the plate from the secondary to the primary position, the diameter of the crank pin circle being greater than the distance between the positions of the crank pin when the switch-plate is in the primary and the secondary positions, whereby rotation of the wheel through an angle less than efiects movement of the plate from the primary to the secondary position, said restoring spring being always effective to urge the plate toward its primary position.

4. A trolley switch frog comprising an elongated body portion, an elongated switch-plate pivoted to the said body portion for angular movement relative thereto in a horizontal plane between primary and secondary positions, a stepped cone wheel having two rims mounted on the body portion adjacent the region of maximum movement of the switch-plate for rotation about a vertical axis, a crank pin on said wheel, a coupling between the said pin and the said switch-plate such that when the switch-plate is in the primary position the pin is in a dead centre position to iereby lock the switch-plate in said primary position a flexible tension member trained around one rim of the wheel and secured at one end thereto whereby to turn the latter and move the plate from primary to secondarypositions, a second flexible tension member trained around the other rim of the wheel and secured at one end thereto, and a restoring spring anchor-ed at one end to said body portion, the other end of the spring being secured to the second flexible tension memher so as to exert a continuous torque thereon tending to move the plate from the secondary to the primary position, the diameter of the crank pin circle being greater than the distance between the positions of the crank pin when the switchplate is in the primary and the secondary positions, whereby rotation of the wheel through an angle less than 180 efiects movement of the plate from the primary to the secondary position, said restoring spring being always eiTectiv-e to urge the plate toward its primary position.

TALBOT COTTOM BROOM. HOWARD JENKINS POWELL. 

